Crush Point

When large crowds assemble, is there a way to keep them safe?

Ninety-five people died in a crush at a soccer match at Hillsborough stadium, in Sheffield, England, in 1989.

Photograph by DAVID GILES / PA WIRE / AP PHOTO

On Thanksgiving Day, 2008, shoppers began lining up outside the Wal-Mart in Valley Stream, Long Island, at 5:30 P.M., near a small, handwritten sign that read “Blitz Line Starts Here.” Like many other retailers holding “doorbuster” Black Friday sales, Wal-Mart was offering deep discounts on a limited number of TVs, iPods, DVD players, and other coveted products. Only two months earlier, the U.S. economy had nearly collapsed, and although the Christmas shopping season was looking dismal, there was still some dim hope that the nation might be able to shop its way out of disaster, as we were advised to do after 9/11.

By two in the morning, the line ran the length of the building, past Petland, turned at a wire fence, and stretched far into the bleak parking lot of the Green Acres Mall, a tundra of frosted tarmac. There were already more than a thousand people. Store managers had placed eight interlocking plastic barriers between the front of the line and the outer doors to the store, to create a buffer zone that would keep people from crowding around the entrance. But at three people began jumping the barriers. The store’s assistant manager, Mike Sicuranza, spoke to the manager, Steve Sooknanan, who had gone to a hotel to rest, and told him that customers had breached the buffer zone. Sicuranza sounded frightened. Sooknanan told him to call the police.

The Nassau County police arrived soon after the call, and, using bullhorns, ordered everyone to get back behind the barriers. The police were still there at four, when Sooknanan returned to the store. Shortly afterward, a Wal-Mart employee brought some family members inside the barriers, angering the crowd. About two hundred shoppers pushed into the buffer zone. Those in front were squeezed against two sliding glass outer doors that led into a glassed-in, high-ceilinged entrance vestibule that also held some vending machines. These had been pushed to the center of the space, to prevent people from crossing it diagonally and entering through the exit doors. As more people gathered, in anticipation of the store’s opening, at 5 A.M., the pressure on the doors built and they began to shake. “Push the doors in!” some chanted from the back.

Employees asked the police for help. According to a court filing, the police responded that dealing with this crowd was “not in their job description,” and they left. Of the two-man security force that Wal-Mart had hired for Blitz Day, only one had shown up, and he was inside the store. Shortly before five, the crowd had grown to about two thousand people. The store’s asset-protection manager, Sal D’Amico, advised Sooknanan not to open the doors, but Sooknanan overruled him. He instructed eight to ten of his largest employees, most of whom worked in the stockroom, to stand at the sides of the vestibule as the outer doors were opened, and be ready to help anyone who tripped or fell.

One of those men was Jdimytai Damour, who lived in Jamaica, Queens; his parents were Haitian immigrants. Damour was thirty-four, and beefy—at six feet five inches tall, he weighed around four hundred and eighty pounds. Friends called him Jdidread, because he wore his hair in dreadlocks. He had been working at Wal-Mart for about a week, as a temporary employee in the stockroom. Like the others in the vestibule, he had no training in security or crowd control. A co-worker had reportedly heard him say earlier, “I don’t want to be here.”

Just before five, the workers realized that a pregnant woman, Leana Lockley, a twenty-eight-year-old part-time college student from South Ozone Park, was being crushed against the glass on the outer doors. The managers slid them open just enough to pull Lockley inside the vestibule. The crowd surged forward, thinking that the store was opening. The workers shut the doors again and braced both sliding doors with their bodies to keep them from caving in, as Sooknanan initiated the festive countdown, a Wal-Mart Blitz Day tradition. Ten, nine, eight . . . At zero, the doors were opened again. There was a loud cracking sound as both sliding doors burst from their frame, and the crowd boiled in.

Dennis Fitch, one of the workers standing at the entrance, was blown backward, through the inner vestibule doors and into the store. Others managed to jump to safety atop the vending machines. Some attempted to form a human chain on the other side of the vestibule, to slow down the crowd rushing into the store. A crush soon developed inside the vestibule, but the people who were still outside, pushing forward, weren’t aware of it. Leana Lockley was carried through the vestibule and into the store by the surge, and she tripped over an older woman, who was on the ground. As she got to her knees, she later said, she saw Damour next to her. “I was screaming that I was pregnant, I am sure he heard that,” she told Newsday. “He was trying to block the people from pushing me down to the ground and trampling me. . . . It was a split second, and we had eye contact as we knew we were going to die.”

Co-workers later testified that Damour was hit by one of the two sliding glass doors. As he went down, the door fell on top of him, and people fell over it. Maybe he got up again to help Lockley, but that’s not clear in camera and cell-phone-video footage of the scene. He just vanishes into the frantic tangle of limbs.

Lockley’s husband, Shawn, was able to pull her out, badly bruised. A healthy girl was born the following April. But though “Big guy down” was broadcast over the walkie-talkies that some of Damour’s co-workers carried, they had to fight their way through the crowd to reach him, and when they got there Damour’s tongue was out and his eyes had rolled back. The cops arrived at 5:05 A.M., and performed CPR (a cell-phone video made its way to YouTube), without success. Damour was pronounced dead at the Franklin Hospital Medical Center, in Valley Stream, at 6:03 A.M. The coroner’s report did not mention any bruises, fractures, or internal injuries, as it would have if he’d been trampled to death; the cause of death was listed as asphyxia.

Crowds are a condition of urban life. On subways and sidewalks, in elevators and stores, we pass in and out of them in the course of a day, without pausing to consider by what mechanisms our brains guide us through so easily, rarely touching so much as a stranger’s shoulder. Crowds are often viewed as a necessary inconvenience of city living, but there are occasions when we gladly join them, pressing together at raves and rock concerts, at sporting events, victory parades, and big sales. Elias Canetti, in his 1960 book “Crowds and Power,” sees these times of physical communion with strangers as essential to transcending the fear of being touched. “The more fiercely people press together,” he writes, “the more certain they feel that they do not fear each other.” In fact, a crowd is most dangerous when density is greatest. The transition from fraternal smooshing to suffocating pressure—a “crowd crush”—often occurs almost imperceptibly; one doesn’t realize what’s happening until it’s too late to escape. Something interrupts the flow of pedestrians—a blocked exit, say, while an escalator continues to feed people into a closed-off space. Or a storm that causes everyone to start running for shelter at the same time. (In Belarus, in 1999, fifty-two people died when a crowd tried to enter an underground railway station to keep dry.) At a certain point, you feel pressure on all sides of your body, and realize that you can’t raise your arms. You are pulled off your feet, and welded into a block of people. The crowd force squeezes the air out of your lungs, and you struggle to take another breath.

John Fruin, a retired research engineer with the Port Authority of New York and New Jersey, is one of the founders of crowd studies in the U.S. In a 1993 paper, “The Causes and Prevention of Crowd Disasters,” he wrote, “At occupancies of about 7 persons per square meter the crowd becomes almost a fluid mass. Shock waves can be propagated through the mass sufficient to lift people off of their feet and propel them distances of 3 m (10 ft) or more. People may be literally lifted out of their shoes, and have clothing torn off. Intense crowd pressures, exacerbated by anxiety, make it difficult to breathe.” Some people die standing up; others die in the pileup that follows a “crowd collapse,” when someone goes down, and more people fall over him. “Compressional asphyxia” is usually given as the cause of death in these circumstances.

Crowd disasters occur all over the world, and for a variety of reasons. According to a recent paper published in the journal Disaster Medicine and Public Health Preparedness, reports of human stampedes have more than doubled in each of the past two decades. In the developing world, they often occur at religious festivals. In November, hundreds of people died in Cambodia, in a crush that occurred on a bridge in Phnom Penh during the annual water festival; there were reports that the police had fired water cannons at people on the crowded bridge. Thousands have died making pilgrimages to Mecca in the past twenty years, mainly in the ritual called the Stoning of the Devil, which occurs near the Jamarat Bridge; in 2006, three hundred and sixty pilgrims were killed there. In India last month, more than a hundred Hindu worshippers died in a crush in the state of Kerala.

In the developed world, soccer games and rock concerts are the most likely events to generate deadly crowds. In 1989, in Sheffield, England, ninety-five people died after they were caught in a crowd crush at Hillsborough stadium when fans were trying to get into a soccer match between Nottingham Forest and Liverpool. (A ninety-sixth victim was taken off life-support four years later.) At a rock festival in Roskilde, Denmark, in 2000, nine people died after a crowd collapse that occurred near the stage while Pearl Jam was performing in front of an audience of fifty thousand. Last July, twenty-one people were killed at the Love Parade, a free electronic-music festival in Duisburg, Germany, when a crush developed in a disused rail tunnel that led to the festival grounds. With the world’s population increasing, and with more people moving to cities, crowds will become ever larger, and disasters more frequent, unless scientists and safety engineers can figure out how to prevent them from happening.

In the literature on crowd disasters, there is a striking incongruity between the way these events are depicted in the press and how they actually occur. In popular accounts, they are almost invariably described as “panics.” The crowd is portrayed as a single, unified entity, which acts according to “mob psychology”—a set of primitive instincts (fear, followed by flight) that favor self-preservation over the welfare of others, and cause “stampedes” and “tramplings.” But most crowd disasters are caused by “crazes”—people are usually moving toward something they want, rather than away from something they fear, and, if you’re caught up in a crush, you’re just as likely to die on your feet as under the feet of others, squashed by the pressure of bodies smashing into you. (Investigators collecting evidence in the aftermath of crowd disasters have found steel guardrails capable of withstanding a thousand pounds of pressure bent by crowd force.) In disasters not involving fire, panic is rarely the cause of fatalities, and even when fire is involved, such as in the 1977 Beverly Hills Supper Club fire, in Southgate, Kentucky, research has shown that people continue to help one another, even at the cost of their own lives.

So why do we still think in terms of panics and stampedes? In many crowd disasters, particularly those in the West where commercial interests are involved, different stakeholders are potentially responsible, including the organizers of the event, the venue owners and designers, and the public officials and private security firms whose job is to insure crowd safety. In the aftermath of disasters, they all vigorously defend their interests, and rarely are any of them held accountable. But almost no one speaks for the crowd, and the crowd usually takes the blame.

The origins of the term Black Friday are obscure. Some think that it was first used by the police in Philadelphia to describe the snarled traffic and sidewalk hassles that came with the day after Thanksgiving and crowds arriving for the city’s annual Army-Navy game. Others have defined Black Friday as the day that merchants’ balance sheets crossed over into the black. Either way, it is now a de-facto national shopping holiday. On TV, images of people racing through the aisles of stores for sale-priced items, in a sort of American Pamplona, have become as much a part of the day after Thanksgiving as leftovers. Shoppers get discounts, programmers get some lively content for a slow news day, and retailers get free publicity: a good deal for everyone, except for the clerks who have to work that day, breaking up fights among shoppers and cleaning up the mess left behind.

There had been injuries on previous Black Fridays, but no one had ever died before Jdimytai Damour went down in the Valley Stream Wal-Mart. His death, and the “Wal-Mart Stampede” that caused it, was the lead story on news channels across the country that evening, and it provoked a vast outcry of horror. In days of commentary that followed, the crowd was widely vilified. The tone of much of the reaction was captured by a letter writer to the New York Post, who blamed “the animals (you know who you are) who stampeded that poor man at Wal-Mart on Black Friday: You are a perfect example of the depraved decadence of society today.”

A Wal-Mart senior vice-president, Hank Mullany, said in a statement, “Our thoughts and prayers go out to the family of the deceased. We are continuing to work closely with local law enforcement, and we are reaching out to those involved.” Investigators would be reviewing video collected from security cameras, and looking at purchases made with credit cards, in an effort to identify individuals who may have witnessed or been involved in Damour’s death. But even if investigators could pick out, amid the flailing limbs and hurtling bodies in the videos, those who had harmed Damour, who could say that he or she wasn’t pushed by the person behind? And, at any rate, the police seemed to be in no mood to “work closely” with Wal-Mart. Rather, they went out of their way to blame Wal-Mart for the incident. Detective Lieutenant Michael Fleming, who was in charge of the investigation into Damour’s death, said at the time, “I’ve heard other people call this an accident, but it is not. Certainly it was a foreseeable act.”

Through the winter and spring of 2009, the Nassau County District Attorney’s office prepared to bring criminal charges against Wal-Mart, for felony reckless endangerment and misdemeanor reckless endangerment. The family of Jdimytai Damour filed a wrongful-death claim against the company. However, in early May, 2009, the county’s District Attorney, Kathleen Rice, announced that her office had worked out a deal with Wal-Mart that allowed it to avoid criminal charges. The company agreed to donate one and a half million dollars to various community projects and to create a four-hundred-thousand-dollar victims’ fund. Wal-Mart also agreed to implement a “crowd management” plan for future post-Thanksgiving Day events at each of its ninety-two New York stores. In return, Wal-Mart would face no charges or criminal liability for the death of Jdimytai Damour. If the company failed to meet the standards set by an independent monitor for three years, the criminal case would be reinstated. Rice, noting that the maximum penalty Wal-Mart would have faced was a ten-thousand-dollar fine, said, “This agreement does more than any criminal prosecution could ever accomplish.” Damour’s father, Ogera Charles, saw things differently. “It’s like if they were driving a car and they hit someone, killed him, and then just walked away,” he told Newsday.

At the end of May, the Occupational Safety and Health Administration cited Wal-Mart for committing a “serious violation” of the General Duty Clause of the OSHA Act. The clause states that an employer must furnish workers with a place of employment that is “free from recognized hazards that are causing or are likely to cause death or serious physical harm to his employees.” In its complaint, OSHA listed the hazards that Damour and his co-workers faced there as “asphyxiation or being struck due to crowd crush, crowd surge or crowd trampling.” The complaint also said that Wal-Mart “did not use appropriate crowd management techniques to safely manage a large crowd of approximately 2000 customers.”

The proposed penalty was seven thousand dollars—not an enormous burden for the world’s biggest retailer, which had total sales of four hundred and five billion dollars in 2010. But Wal-Mart elected to contest the citation, and hired the Washington, D.C., law firm of Gibson, Dunn & Crutcher to handle the litigation. Wal-Mart objected on multiple grounds. First, if crowd crushes and surges were recognized hazards, then why hadn’t a single OSHA General Duty Clause citation ever referred to the dangers posed by crowds before? Wal-Mart also maintained that it had taken steps to protect its workers from the crowd, but it could not have protected workers from this particular crowd. And, finally, the violence caused by the crowd was a police issue and therefore beyond OSHA’s jurisdiction.

A federal administrative-law judge, Covette Rooney, of the Occupational Safety and Health Review Commission, was assigned to the case, but it did not come to trial for more than a year. Wal-Mart’s lawyers filed twenty pretrial motions and responses, and spent, by OSHA’s calculations, two million dollars fighting the citation. In all, OSHA lawyers invested around five thousand hours in the case. Why was Wal-Mart fighting a paltry fine so hard? To the extent that the citation could strengthen the Damour family’s civil case, two million dollars could be seen as a worthwhile gamble. Moreover, no retailer welcomed OSHA jurisdiction over how it managed its customers. Casey Chroust, an executive vice-president of the Retail Industry Leaders Association, told me, “The impact of this case is potentially huge. Does it mean I have to hire an event-management staff next time I hold a doorbuster sale? Does this mean every time you have a hot product—a video game, a Harry Potter book, an iPhone—much less a Black Friday sale, you’ll be liable for potential action if you don’t hire crowd management?” Willis Goldsmith, a partner at the New York firm of Jones Day, who has a long history of representing employers on OSHA issues, told me that, along with the problem of defining crowd surges and crushes as recognized hazards, there was the practical matter of defining a crowd. “Ten people could have caused the injuries you saw at Wal-Mart. So is that a crowd?”

OSHA’s burden was to prove that crowd surge and crowd crush are well-known phenomena, and that crowd-management techniques could have prevented them at the Green Acres Mall. To do that, it needed to find an expert who would testify against Wal-Mart. Most experts in the field consult for private industry—event planners and promoters, venue owners and operators, and, to a lesser extent, large retailers. Even if they agreed with OSHA, testifying against the world’s largest retailer wasn’t likely to be good for business, and many experts wouldn’t do it. But one would: Paul Wertheimer, the sixty-two-year-old self-employed owner of Crowd Management Strategies, who has been called “the marshal of the mosh pit.”

One of the best-documented crowd disasters in the U.S. occurred before a concert by The Who, outside Riverfront Coliseum in Cincinnati, on December 3, 1979. Until then, crowd planning had largely been the purview of fire-safety engineers, who focussed on how to get people out of buildings, in the event of an emergency—not into them. The concert’s promoter, the Electric Factory of Philadelphia, had offered unreserved “festival seating”—people in the front of the line get to be nearest the stage (and, in most cases, no one on the floor has a seat at all, allowing the promoter to sell more tickets but giving the venue far less control over the audience). Hard-core fans began lining up in the early afternoon, and by six o’clock a crowd of eight thousand mostly young people had collected on the plaza outside the entrance, on a bitterly cold night. The band began its sound check at around six-thirty, and played for half an hour. People toward the back of the line, mistakenly believing that the concert was beginning, pushed forward. Some of the people in front pushed back, and shock waves began to ripple through the tightly packed mass. The coliseum staff, thinking that the crowd was attempting to rush the doors and enter without paying, kept most of the doors shut, even after the sound check ended and the opening time had passed.

Later, in a letter sent to the task force assembled to investigate the incident, in which eleven people died, a man in the crowd described what it was like near the doors: “The pounding of the waves was endless. . . . If a wave came and you were being stood upon with your feet pinned to the ground, you would very likely lose your shoes or your balance and fall.” Some people near the doors did go down. “They began to fall, unnoticed by all but those immediately surrounding them. People in the crowd 10 feet back from them didn’t know it was happening. Their cries were impossible to hear above the roar of the crowd. . . . There was a pile of people forming, and all of the people around them were being crushed into the pile, for there was no resistance. If the person in front of you went down, then you would follow for there was no one to lean against.” Then the waves began to carry him toward the pile. “With this realization I began to add to the screaming, ‘They’re going down, they’re going down!’ I yelled repeatedly. . . . A wave swept me to the left and when I regained a stance I felt I was standing on someone. The helplessness and frustration of the moment sent a wave of panic through me. I screamed with all my strength that I was standing on someone. I couldn’t move. I could only scream.”

The media blamed the crowd. The Lexington, Kentucky, Herald-Leader, describing the “surging, primitive mob,” quoted a security guard who said, “Those kids were animals.” Mike Royko wrote a column for the Chicago Sun-Times, entitled, “Cincinnati Barbarism: A Rockwork Orange,” blaming the “barbarians” who “stomped 11 persons to death [after] having numbed their brains on weeds, chemicals, and Southern Comfort.” The promoter, Larry Magid, told Rolling Stone, “After all, we didn’t trample anyone to death, we didn’t step on anyone, and we didn’t push anyone.” Pete Townshend, the band’s leader, said, “It’s rock. It’s not The Who. It’s rock and roll. Everybody—all of us—we’re all bloody responsible.” In the end, no one was held accountable for the deaths.

At the time, Paul Wertheimer was a twenty-nine-year-old public-information officer for the city of Cincinnati. He became chief of staff of the task force that Mayor Kenneth Blackwell appointed to investigate the incident. Wertheimer and some of his staff members spent months travelling around the country, talking to venue operators and promoters and public-safety officials. Among the task force’s recommendations were a ban on festival seating for large indoor events, and a requirement that organizers file a “crowd management” plan, similar to a fire-safety plan, but focussing on ingress as well as egress. The report pointed out that doors and turnstiles in buildings of public assembly were tested only for normal conditions, and failed to take crowded conditions into account. It also called for national standards to better protect crowds. But national standards weren’t created and festival seating wasn’t universally banned. Injuries and fatalities at concerts continued.

As Wertheimer worked at various jobs in event management and public relations, “the Who tragedy kept following me around,” he recalled. “Every now and then, another incident would happen at a concert, someone would get killed, and the reaction was always the same. The industry would say, ‘How could we have predicted this? This has never happened before!’ And of course I would say, ‘That’s not true—it did happen, and here’s a report about it!’ But the industry chose to ignore that. And I thought, Somebody has to step up and do something, because there are ways to prevent these people from dying. And I guess that guy is going to be me. I am going to be the ghost of that Who concert. Those eleven people died so that these lessons could be learned, and I’m going to see they aren’t forgotten.”

Wertheimer began carefully documenting crowd-related incidents in the U.S. and around the world, making the information available to the public. He ventured into potentially dangerous crowds, wherever he could find them, and noted what he saw. In the early nineties, with the popularity of grunge music, mosh pits became common at rock concerts—fans in the front would hurl themselves at one another, and the force would carry them into other fans. Mosh pits are good places to study crowd dynamics, because they reproduce in miniature the shock waves of large-scale crowd disasters. Wertheimer, in his early forties, became a familiar figure at grunge and heavy-metal shows: “the old man in the pit,” in the words of one young fan. “I learned how to stand in the center spot,” he told me proudly, “right in front of the lead singer, three yards from the stage, and to go with the surge, and I developed my ways of getting out of tight spots, which I published in my mosh-survival guide. I worked on my peripheral vision, and learned to recognize when people are in trouble, and to understand what draws them to moshing, and how the band relates to it, and what security does in certain situations—all that stuff.” He established a Web site, Crowd Safe, where he published his reports on crowds, which eventually numbered in the thousands.

As predicted, none of this helped Wertheimer’s career as a crowd-management consultant; his pugnacious personality didn’t help, either. “The industry didn’t want anything to do with me,” Wertheimer told me. In Chicago, where Wertheimer was born, on the South Side, he ran afoul of a concert promoter, Jam Productions, for helping to publicize safety issues at rock concerts. (Wertheimer brought a local news reporter, with a concealed camera, into the mosh pit at a show put on by Jam, and pointed out the unsafe conditions. Jam contends that the footage was misleading.) Jam posted his photograph around Soldier Field, and during a Pearl Jam concert Wertheimer was picked up in a mosh pit by security for apparently shoving a young fan. “Obviously, if I wanted to develop a consulting business, this wasn’t the way to do it,” he told me.

After the deaths of the nine festival-goers during the 2000 Pearl Jam set in Roskilde, Wertheimer was interviewed by a committee set up by the Danish government, and recommendations he made became a part of the committee’s official report, “Rock Festival Safety.” He was delighted when OSHA asked him to testify in the Wal-Mart case. “This is the most important thing I’ve ever been involved with,” he said. “For the first time, you’ve got someone powerful—the U.S. federal government—alleging that this death was preventable, if the crowd had been handled the right way.” Was he anxious about the trial? “I know you can pay a price if you take on a large corporation like Wal-Mart. You have to be willing to suffer the consequences. I don’t have kids to support, or a family; this is the role I take. I’m the only one who would do this. And, hey, I learned to fight on the South Side.”

During the years that Wertheimer was recording his experiences at rock concerts, researchers in academia were trying to figure out models for crowd behavior. In the early nineties, Dirk Helbing, a graduate student in physics at the University of Göttingen, Germany, was looking for a suitable topic for a diploma thesis, when he was inspired by footprints left in the snow after a large event. He saw a pattern in the tracks that suggested the flow of streams, and he came up with a model based on fluid dynamics to simulate crowd movement. By comparing computer-driven simulations with empirical observations of crowd movement, Helbing and his colleagues were able to identify several patterns of collective behavior that emerged from the interactions of individuals in the crowd. These included lanes of uniform walking directions, oscillations of the pedestrian flow at bottlenecks, and “stripes” of intersecting flows. “Such self-organized patterns of motion demonstrate that efficient, ‘intelligent’ collective dynamics can be based on simple, local interactions,” Helbing wrote in a 2010 paper, “Pedestrian, Crowd, and Evacuation Dynamics,” published in the “Encyclopedia of Complexity and Systems Science.”

But Helbing also observed that at certain critical densities, such as occur in a crowd crush, all forms of collective behavior vanish. Shock waves are the result not of collective behavior but of the failure of it. Individuals at the back of a crowd, unable to tell what is happening up ahead, push forward, not realizing that they are injuring the people in the front. Unlike ants and fish and birds, humans haven’t evolved the capability to transmit information about the physical dynamics of the crowd across the entire swarm. Ants, for example, are able to communicate within a swarm using pheromones. Iain Couzin, a behavioral biologist at Princeton University, told me, “With ants, as with human crowds, you see emergent behavior. By using a simple set of local interactions, ants form complex patterns. The difference is that we are selfish individuals, whereas ants are profoundly social creatures. We want to reduce our travel time, even when it is at the expense of others, whereas ants work for the whole colony. In this respect, we are at our most primitive in crowds. We have never evolved a collective intelligence to function in large crowds—we have no way of getting beyond the purely local rules of interaction, as ants can.”

So is there no possibility that a crowd of bodies can be “smart,” in the sense that a crowd of minds can be? Couzin pointed to the role that “leaders” play in the sudden movements of schools of fish, or in migratory herds of animals: only a few of the animals possess the necessary information about where to go, but the others spontaneously follow them. In 2005, he helped design an experiment at Leeds University, led by Jens Krause, in which two hundred people were told to walk randomly around a large hall, while a few people were given specific instructions about what route to take. The researchers found that the “naïve” group followed the informed “leaders,” even though they had no idea, in most cases, that they were following leaders at all. “Leadership does not require verbal communication,” Couzin told me. Studies of disaster evacuations, including the 2001 World Trade Center bombing, have shown that people who follow well-informed leaders might stand a better chance of escape than people who delay or seek their own way out, but in a crowd crush that isn’t going to help much. The leaders will be hemmed in, too.

The Wal-Mart trial took place during six very hot days in July, 2010, in a courtroom in the Jacob Javits Federal Building, in lower Manhattan. Four Wal-Mart employees, who had been at the entrance of the vestibule with Jdimytai Damour, testified. Justin Rice, who had been promoted to department manager before Black Friday, 2008, and who was still working at the store, said that the doors had broken on Blitz Day in 2007, and he had been nicked by broken glass. (Another employee said that the doors came off the hinges in 2005 and 2006, as well.) All the men said that they had never had any training in crowd management before being placed in the vestibule on November 28, 2008, except for “slip, trip, and fall” guidelines—if a customer slips, you help him up—and the “ten-foot rule,” which is if a customer gets within ten feet you are supposed to greet her with “Welcome to Wal-Mart.”

One particularly damning bit of evidence was a video that students from the New York Institute of Technology had chanced to make of a management meeting two days before the Blitz Day event. Rice can be heard raising the matter of the 2007 melee with Steve Sooknanan, the Wal-Mart manager, and saying that people had to be kept away from the doors this year. He says, “Last year was crazy, a lot of people fell, little babies out there and it was cold, I just don’t want that this year.” Sooknanan tells him that this year “we’re going to do it a little differently.” He explains that he had arranged for construction barriers to be placed farther from the entrance and to have additional staff at the door.

Jason Schwartz, the lead trial attorney for Wal-Mart, wasted no time in attacking Paul Wertheimer’s qualifications as a crowd expert—“the dubiously monikered ‘marshal of the mosh pit’ ”:

J.S.: What do you do when you’re in a crowd, Mr. Wertheimer, in order to enhance your expertise?

P.W.: I observe the crowd, the crowd dynamics, the crowd behavior, and people in the crowd and talk to people in the crowd to see how they’re feeling, see what’s going on.

J.S.: If I did that, would I have the same level of experience in crowds as you do?

P.W.: No.

J.S.: Why not?

P.W.: You’re not an expert in the area of crowd management.

J.S.: I see. . . . Your Honor, I would submit that this expert’s qualifications are the same qualifications that everyone standing in this courtroom has.

Judge Rooney responded, “But he has more experience in crowds than I do. I don’t take subways, so I have no idea what it’s like to be in a crowd. Well, I could say, back in my days of college, I took the subway here in New York, and I was very claustrophobic. So I do believe that there is some assistance that, or some value that, is going to be elicited from this case.”

Wertheimer was allowed to continue, and during two days of testimony detailed many crowd measures that Wal-Mart could have taken. He was particularly effective in showing why the construction barriers wouldn’t control the crowd: they were too low to keep people out, and they were flared at the bottom, so that people who got pushed up against the sides fell in.

At the end of six days, Judge Rooney had twelve hundred pages of testimony to deliberate over, which she has done, at a stately pace, for the past six months. Both sides eagerly await the verdict, which is expected soon. If OSHA wins, Wal-Mart will almost certainly appeal—all the way to the U.S. Court of Appeals, if necessary. Still, a decision for OSHA will have enormous symbolic value, because it would be a victory for the crowd.

In the past thirty years, safety officials and designers have learned a lot about crowd management. After the Hillsborough disaster, Britain banned standing terraces in its top two soccer divisions, and introduced “all-seater” stadiums. Some people argued that this changed the atmosphere of the games profoundly, but it also made them safer. An international team of experts, including Keith Still, a professor of crowd dynamics, made recommendations for the redesign of the Jamarat Bridge, in Mecca, and for directing the movement and flow of people. The structure has been altered to provide pilgrims with multiple entrance and exit points, to ease congestion. In Times Square on New Year’s Eve, the police use lightweight metal container pens so that people revel inside a series of small enclaves, rather than as one big mass. Crowd managers use elevated viewing platforms, to see over the crowd, and, if necessary, to communicate with people in the back. Paul Wertheimer has written a booklet, “You and the Festival Crowd,” which has been widely distributed. (Among his recommendations: Keep your elbows akimbo, to protect your chest and give yourself enough breathing room. Don’t fight against the flow of the crowd if you’re trying to get out of it; rather, go with it, and during lulls try to work your way diagonally through the crowd to the perimeter. If you feel faint, grab on to someone, and, if you do fall, try to protect your head.)

And yet, almost anywhere, you can be trapped in a crowd: on a subway platform, at the lighting of the Christmas tree in Rockefeller Center, on the ramps leading down from the upper tiers at Yankee Stadium, in the Halloween Parade in Greenwich Village. One reason last summer’s Love Parade disaster in Germany was so shocking is that it occurred in a country known for efficient crowd management, and yet the early evidence suggests that the organizers and the police made a series of elementary mistakes, including underestimating the number of attendees, using the railway tunnel as both the main entrance to and the main exit from the event, and blocking the flow of concertgoers at pinch points, which allowed the crowd force to build. A full-scale investigation is under way.

A light rain was falling over the parking lot at the Green Acres Mall when I pulled in, at three in the morning, on Black Friday, 2010. The longest line was at Best Buy—it stretched the length of the building and halfway down the other side. The people in front had been waiting for twenty-eight hours. “Wii Bundles,” one man said, when I asked why, as though the answer were obvious. Target also had a long line outside, and there were smaller lines outside Kohl’s and Macy’s. But outside Wal-Mart there was no line at all.

After Black Friday, 2008, Wal-Mart dropped the term Blitz Day, and rebranded its post-Thanksgiving Day sale The Event. In keeping with the terms of its agreement with the Nassau County D.A.’s office, the company employed a crowd-management plan at all its New York stores. In Valley Stream, there were more staff, security, and crowd managers outside the store than there were customers. I snaked through the barricades—metal, chest high, with open bottoms—that had been arranged in a series of tight S curves, passing two viewing platforms, with a man on each holding a bullhorn welcoming me. I entered the vestibule where Damour died, remembering the images of chaos I had seen in the videos of that night. Perhaps the most horrifying aspect of those videos is the sound inside the vestibule: cries of pain, fear, terror, mayhem. But now it was eerily quiet.

This year, like last, the waiting took place inside the store, which remained open all night. Beginning at midnight, the store began distributing tickets for the steeply discounted electronic items, and by three-fifteen they had all been given out. People arriving when I did weren’t happy. “You said the sale starts at five. That’s false advertising,” one irate customer said to a manager. “It’s not me, it’s them,” the manager said, gesturing toward the ceiling. People were lining up anyway for the ordinary sale-priced items, but there was no joy of the hunt in the line. It was just a line. ♦

John Seabrook has been a contributor to The New Yorker since 1989 and became a staff writer in 1993.